In the parent application, there is provided a hydrostatic valve, particularly in FIGS. 8 and 10 of said application. The valve is employed with hydraulic motors, see FIG. 1 (FIG. 7 of the parent application, the description of which is incorporated herein by reference) configured to prevent creep of, primarily, riding type lawn mowers when the mower is in an idling condition. The valve of the aforesaid application reduce the problem of the mower moving suddenly, jumping, when the hydraulic pump employed to provide working fluid to the vehicle's hydraulic motor, is first turned on.
The prior application provided a ball valve, FIGS. 2 and 3 (FIGS. 8 and 10 of the parent application, the description of which is incorporated herein by reference) that responds automatically to changes in hydraulic pressure. Initially, under idling conditions the valve is open and permits oil under low pressure to drain directly to the oil tank and the hydraulic motor is not driven. Specifically, the ball floats in the open position maintaining flow to the oil tank. As pointed out in the parent application, if the swash plate of the pump is not properly set the pressure supplied will cause the mower to creep. In the parent case, the ball of the valve floats during low pressure periods having a closing threshold above that normally encountered as a result of an improperly adjusted swash plate.
A problem may arise, however, if the pump is returned to idling condition and then started up again. When the pump is returned to the idling condition, the ball floats and when high pressure is applied again, the mower may jump.